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Cost-effectiveness of iron supplementation and malaria chemoprophylaxis in the prevention of anaemia and malaria among Tanzanian infants |
Alonso Gonzalez M, Menendez C, Font F, Kahigwa E, Kimario J, Mshinda H, Tanner M, Bosch-Capblanch X, Alonso P L |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology Iron supplementation and malaria chemoprophylaxis (Deltaprim) in the prevention of anaemia and malaria.
Study population Infants aged under 1 year of age.
Setting Interventions took place within the community. The economic evaluation was carried out within the structure of the Expanded Programme on Immunisation in Kilombero District, United Republic of Tanzania.
Dates to which data relate Effectiveness and cost data related to 1996, although some effectiveness data were not dated. The price year was 1996.
Source of effectiveness data The main evidence/estimate for the final outcome was derived from a single study, but published sources and expert opinion were used to estimate other necessary effectiveness data.
Link between effectiveness and cost data The costing was obtained on the same patient sample as that used in the effectiveness study. It was not stated whether the costing was undertaken retrospectively or prospectively.
Study sample Patients were identified through passive detection as well as cross-sectional surveys of infants aged 8-52 weeks. The method of randomisation, power calculations and sample size were not specified.
Study design The study design was a randomised-controlled trial. The duration of follow-up and losses to follow-up were not reported. The method for assessment of outcomes was not reported.
Analysis of effectiveness The analysis of the clinical study was based on intention to treat analysis. The primary health outcome was the incidence of severe anaemia or clinical malaria. Further estimates of effectiveness required for the economic evaluation were life expectancy taken from Life Tables, case fatality rates from severe anaemia and first clinical malaria episodes, estimated from a prospective cohort of hospitalised children in the same area and the mean duration of episodes, estimated from the literature and from expert opinion.
Effectiveness results Effectiveness results were reported in terms of percentage reductions in the incidence of severe anaemia or clinical malaria with regard to the control group. In brackets are the lower effectiveness estimates calculated using the lower 95% confidence interval further adjusted for 20% loss in attendance at second visit. The percentage reductions in incidence of severe anaemia were 68.5% (52.3%) for Deltaprim+iron, 59.8% (41.1%)for Deltaprim alone and 32.1% (4.6%) for iron alone. The percentage reductions in first episodes of clinical malaria were 65.9% (39.7%) for Deltaprim+iron and 59.4% (32.9%) for Deltaprim alone. Case fatality rates were 6.1% for severe anaemia and 4.7% for malaria. The mean duration of episodes of treated severe anaemia and of malaria was determined as 3 months and 28 days respectively.
Clinical conclusions Deltaprim+iron was the most effective strategy for all effectiveness estimate assumptions.
Measure of benefits used in the economic analysis Benefits were measured in terms of disability-adjusted life-years (DALYs) saved per intervention. Disability weights were taken from a previous study, but no further information was provided as to how these were derived. DALYs were discounted at 3%.
Direct costs Discounting was not applied because a one year period for costs was used. Quantities and costs were not reported separately. Direct costs for the preventive interventions included the costs of preventive interventions for health care providers, the treatment costs for severe anaemia and malaria episodes (not prevented) for health care providers and the household costs of treating severe anaemia and malaria episodes (not prevented) for families. Results were reported from the perspective of the health care provider and from that of society. The cost of preventive interventions for health care providers included personnel costs (health worker and supervisor), costs of driver, stationery, vehicle hire and running costs, the cost of drugs, and capital costs for training. Costs for iron were taken from UNICEF, cost of Deltaprim from Zimbabwe pharmaceuticals, and other costs from the district health office in Tanzania. A 2% discount rate was applied to costs not directly available for 1996. The cost of treatment of severe anaemia and malaria episodes for the health care provider included consumable costs (drugs and laboratory material), personnel costs, other hospital overheads and capital costs (buildings and equipment). The source of costs was the district hospital. The household costs of the treatment of severe anaemia and malaria episodes were not detailed. Costs were estimated from a specific questionnaire administered to 618 mothers of children with clinical diagnosis. The price year was 1996.
Statistical analysis of costs A statistical analysis of costs was not conducted.
Indirect Costs Indirect costs to the household for the treatment of severe anaemia and malaria episodes were included in the study. The nature and the detail of quantities and costs were not reported. Costs were estimated on the basis of the specific questionnaire administered to 618 mothers. The cost of time lost was calculated on the basis of the minimum Tanzanian wage of 17,500 shillings (approximately $30) per month.
Currency Costs were estimated in Tanzanian shillings and converted to US dollars ($) at mid-1996 exchange rate.
Sensitivity analysis Univariate sensitivity analysis was conducted on the estimate of effectiveness by using the lower 95% confidence interval further adjusted for the drop in compliance at the second visit. Changes in the percentage of cases of severe anaemia and clinical malaria treated with standard case management were also tested. Two-way sensitivity analysis was conducted on the effectiveness of standard case management strategy (from lowest to highest possible health gain) and cost of case treatment.
Estimated benefits used in the economic analysis Benefits measured in terms of DALYs averted between standard case management and the preventive interventions for severe anaemia were 2,054 DALYs averted for Deltaprim+iron, 1,794 DALYS averted for Deltaprim and 963 DALYs averted for iron. For first episodes of clinical malaria, the number of DALYS averted were 1,759 for Deltaprim+iron and 1,585 for Deltaprim compared to standard case management. The duration of benefits from the intervention and from the comparator was life time, as provided by standard life expectancy tables. It was assumed that there were no sequelae for infants surviving anaemia or malaria. The possible development of resistance to drugs for the treatment of malaria was not taken into account.
Cost results Costs were reported for the reference population of 2,322 infants. For severe anaemia, the total cost for the health care provider was $23,600 for standard case management, $16,211 for Deltaprim+iron, $15,909 for Deltaprim and $20,143 for iron. The total cost for the health care provider and the household was $30,164 for standard case management, $18,280 for Deltaprim+iron, $18,547 for Deltaprim and $24,600 for iron. For the first episode of clinical malaria, the total cost for the health care provider was $24,152 for standard case management, $16,998 for deltaprim and iron, $16,229 for Deltaprim. The total cost for the health care provider and the household was $31,638 for standard case management, $19,548 for Deltaprim+iron, $19,269 for Deltaprim.
Synthesis of costs and benefits Average cost-effectiveness ratios were reported for each intervention and for both conditions, which is methodologically inappropriate. Incremental cost-effectiveness ratios were calculated for Deltaprim+iron compared to Deltaprim alone for severe anaemia and for malaria. This ratio was $1.2 per DALY averted for Deltaprim+iron compared to Deltaprim alone for the prevention of severe anaemia and $4.4 per DALY averted for Deltaprim+iron compared to Deltaprim alone for the prevention of the first episode of clinical malaria. The results were sensitive to the number of cases of disease treated in the health system. The authors concluded that the three intervention strategies for the prevention of severe anaemia and malaria in infants appeared to be highly cost-effective with the combination of Deltaprim and iron being the most cost-effective.
CRD COMMENTARY - Selection of comparators The choice of the comparator as standard case management for cases of malaria and anaemia not prevented was justified as it was the main strategy for the control of the diseases in the setting of the economic evaluation.
Validity of estimate of measure of benefit Effectiveness data were based on a randomised-controlled trial which was appropriate for the study question. The study sample was representative of the study population. Information on sample size, power calculations, methods of randomisation and blinding were not reported in this article, although they have been published elsewhere. The duration of follow-up from which effectiveness estimates were derived was reported by the authors as being relatively arbitrary and represented one of the major difficulties they encountered in this part of the analysis. Effectiveness estimates from other sources were used in order to calculate DALYs, in particular the estimates of case fatality rates were obtained from a prospective cohort of hospitalised children in the same area about which little information was reported, including whether the two populations were comparable. No information was provided on the method of elicitation of disability weights, including their value.
Validity of estimate of costs All relevant categories of costs were included in the analysis, the study provided a detailed and thorough estimation of direct costs from the perspective of the health care provider. However, no information on the nature of the resources consumed by the household was provided, which weakened the indirect costs analysis. Costs and quantities were not reported separately. A sensitivity analysis of costs was performed, but, from the costs reported in the sensitivity analysis, it was not possible to infer which cost variables had been modified. Appropriate currency conversions were performed. Discounting was unnecessary since costs were incurred within one year.
Other issues The main problem in the study was the reporting of average cost effectiveness ratios when the correct analysis should only consider incremental cost effectiveness ratios which indicate how much more needs to be paid for the incremental gain in health benefit. In this analysis, incremental ratios need not be calculated between standard management and either of the three preventive strategies, since the former was a dominated intervention (i.e. more costly and less effective) in the comparison with any of the three interventions. However, in the comparisons between the three preventive interventions, iron supplementation alone was also dominated by the other two strategies, since it was more costly and less effective. Reporting an incremental cost-effectiveness ratio in this case was incorrect. Appropriate comparisons were made with findings from other studies and the issue of generalisability to other settings was addressed. Limitations of the study acknowledged by the authors included the need to take into account the possible development of resistance to antimalarial drugs.
Implications of the study The authors recommended the inclusion of both malaria chemoprophylaxis and iron supplementation delivered through EPI as a means of improving the control of malaria and anaemia in infants in sub-Saharan Africa. Further research is also required to study the possible development of resistance to antimalarial drugs.
Source of funding Supported by grants from the Fondo de Investigaciones Sanitarias (FIS 95/863), the Spanish Agency for International Cooperation, and the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases.
Bibliographic details Alonso Gonzalez M, Menendez C, Font F, Kahigwa E, Kimario J, Mshinda H, Tanner M, Bosch-Capblanch X, Alonso P L. Cost-effectiveness of iron supplementation and malaria chemoprophylaxis in the prevention of anaemia and malaria among Tanzanian infants. Bulletin of the World Health Organization 2000; 78(1): 97-107 Indexing Status Subject indexing assigned by NLM MeSH Anemia, Iron-Deficiency /economics /prevention & Antimalarials /economics /therapeutic use; Case Management /economics; Cost-Benefit Analysis; Humans; Infant; Infant, Newborn; Iron /economics /therapeutic use; Malaria /economics /prevention & Tanzania; control; control AccessionNumber 22000000566 Date bibliographic record published 31/01/2001 Date abstract record published 31/01/2001 |
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